Optical imaging systems typically include a transmissive or a reflective liquid crystal display (LCD) imager, also referred to as a light valve or light valve array, which imposes an image on a light beam. Transmissive light valves are typically translucent and allow light to pass through. Reflective light valves reflect the input beam into different directions or polarization states in order to form an image.
Many LCD imagers rotate the polarization of incident light. In other words, polarized light is either reflected by the imager with its polarization state substantially unmodified for the darkest state or with a degree of polarization rotation imparted to provide a desired grey scale. A 90° rotation provides the brightest state in these systems. Accordingly, a polarized light beam is generally used as the input beam for LCD imagers. A desirable compact arrangement includes a folded light path between a polarizing beam splitter (PBS) and the imager, wherein the illuminating beam and the projected image reflected from the imager share the same physical space between the PBS and the imager. The PBS separates the incoming light from the polarization-rotated image light. A conventional PBS used in a projector system, sometimes referred to as a MacNeille polarizer, uses a stack of inorganic dielectric films placed at Brewster's angle. Light having s-polarization is reflected, while light in the p-polarization state is transmitted through the polarizer.